<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport"
    content="width=device-width, initial-scale=1.0,maximum-scale=1.0, minimum-scale=1.0, user-scalable=no">
  <title>Document</title>
  <style>

  </style>
</head>

<body>

</body>
<script>
  let data = [
    {
      "month": "1月",
      "salary": 13200
    },
    {
      "month": "2月",
      "salary": 20500
    },
    {
      "month": "3月",
      "salary": 23100
    },
    {
      "month": "4月",
      "salary": 17600
    }
  ]

  let arr = data.map(item => {
    return item.salary
  })

  // let arr = data.map(item => item.salary)
  console.log(arr);
</script>

</html>